Catalytic conversion of shale oil hydrocarbons



Apnl 21,'Y 1953 L. BERG 2,635,987

CATALYTIC CONVERSION OF SHALE OIL HYDROCARBONS Filed April "7, 195o A TTORNEVS Patented pr. 21, 1953 UNITED STATES ATENT OFFICE CATALYTIC CGNVERSION F SHALE GIL HYDROCARBONS Lloyd Berg, Bozeman, Mont., assgnor to Phillips Petroleum Company, a corporation of Delaware 7 Claims.

This invention relates to a process for the conversion of hydrocarbons. In a specific aspect this invention relates to a process for the catalytic poly-forming of a gas oil obtained from oil shale deposits to obtain an improved gasoline fraction therefrom.

Oil shale is a stratified rock formed from mud and organic matter laid down on the floor of ancient seas and lakes. Later,` upheavals of the ocean bottom, followed by water erosion, have laid bare these tremendous seams of oil shale. Development of oil shale resources has not been of commercial interest because it was felt that oil resulting from the mining of oil shale could not be produced as cheaply as it can be produced from the normal petroleum crude sources, and it was also felt that the production of acceptable end products from shale oil was. considerably more expensive than from petroleum crude oil. As a result of the gradual decline of petroleum resources, considerable interest in the mining and processing of oil shale has recently been demonstrated.

Oil is present in the shale as a brown to black solid organic material called kerogen. The oil is extracted in retorts by burning part of the kerogen to furnish the heat necessary to crack the rest of the kerogen and to distill olf the resulting vapors. The cracked vapors are con densed into a very viscous crude shale oil similar in some physical properties to heavy crude petroleum. The crude shale oil has been fractionated and given some of the more common petroleum treatments which have resulted in the production of gasoline, diesel oil and other fuels. These fuels are characterized by a high gum content, high degree of unsaturation, high sulfur and nitrogen content, low color stability, and an oiensive odor suggesive of pyridine, picolines or collidines. From these results it would seem that the usual refining processes are not suitable for the processing of shale oil fractions from the standpoint of the quality of the product. In fact, this is actually true. Conventional petroleum treatment, particularly catalytic and thermal cracking, of gas oil fractions of shale oil produces a gasoline that rapidly deteriorates into an opaque, dark brown to black liquid. This dark liquid can be distilled or similarly treated to obtain a water-white gasoline, but in a matter of days this latter product again assumes a similar dark color. Catalytic and thermal cracking processes are presently used to convert petroleum fractions into gasoline and other lower boiling hydrocarbons. Catalytic cracking processes produce better yields per pass of high octane gasoline than thermal cracking processes, and the former produces greater yields of low molecular weight unsaturated hydrocarbons for use in the manufacture of synthetic rubber and aviation or polymer gasoline than the latter. However, when applied to the treatment of gas oil derived from shale oil, both processes produce a highly unsatisfactory gasoline product.

It is an object of this invention to provide a novel process for producing gasoline from shale oil.

It is another object of this invention to provide a process for treating a gas oil fraction of shale oil to obtain a gasoline whose color does not deteriorate.

It is another object of this invention to provide a process for treating a gas oil fraction of shale oil to obtain improved yields of gasoline.

Further and additional objects of my invention will be readily apparent from the disclosure hereinbelow.

I have found that it is possible to produce from a gas oil fraction of shale oil a gasoline that does not deteriorate and darken in color by contacting the gas oil with a reforming or cracking catalyst in the presence of a normally gaseous hydrocarbon. In accordance with my invention, it is possible to produce gasoline from a gas oil fraction of shale oil in greater yields as compared with catalytic cracking, and the gasoline resulting from the practice of my invention is of improved quality since it retains its water-White color.

The gas oil for my process is obtained from shale oil by conventional methods. For example, the shale oil is treated thermally in retorts to crack the kerogen and to distill olf the resulting vapors. These vapors are recovered and fractionated to obtain a gas oil fraction generally boiling above the gasoline fraction. In general, the gas oil fraction for my process boils within the range of to 450 C., preferably 200 to 370 C. A suitable gas oil fraction that I have employed had a boiling range of 210 to 320 C. The gas oil thus obtained from shale oil is then passed over a reforming or cracking catalyst in the presence of a normally gaseous hydrocarbon at an elevated temperature and pressure. This step is termed catalytic polyforming, and the product therefrom is fractionally distilled to obtain a fraction boiling within the gasoline boiling range. Lower and higher boiling fractions of the prod- -uct may then be recycled to the catalytic polyforming reaction zone for further production of gasoline.

The temperature at which the catalytic polyiorming reaction is eilected is usually within the range of 200 to 700 C., preferably 350 to 500 C. The space velocity of the gas oil feed varies from 0.2 to 20, preferably 0.5 to 10, liquid volumes of gas cil per volume of catalyst per hour. At a given temperature level the rate of conversion of the gas oil tends to decrease as the space velocity of the gas oil is increased. Therefore, at low temperatures low space velocities are employed, and at high temperatures high space velocities are employed. This correlation of temperature and space velocity is required, because the higher temperatures tend to increase the rate of carbon deposition on the catalyst but the higher space velocities tend to reduce the rate of carbon deposition. The carbon that is deposited on the catalyst results from the cracking of the gas oil. When employing isobutylene as the normally gaseous hydrocarbon in my process, maximum yields of gasoline are obtained at temperatures below 450 C. with a space velocity below 2.0 liquid volumes of gas oil per volume of catalyst per hour. At temperatures of 450 C. and higher, maximum yields of gasoline are obtained at space velocities of 2.0 and higher liquid volumes of gas oil per volume of catalyst per hour.

The catalytic polyforming reaction is effected at a superatmospheric pressure, preferably at Vleast 300 pounds per square inch. Pressures Within the range of 800 to 2500, preferably 800 to 1500, pounds per square inch are effective.

The outside gases that are employed in my process are normally gaseous hydrocarbons, either saturated or unsaturated, containing more than one and less than ve carbon atoms per molecule. The C3 and C4 hydrocarbons are preferred, and the most preferred species is isobutylene. Also, mixtures of normally gaseous hydrocarbons of less than five carbon atoms per molecule with or without hydrogen are effective outside gases. In particular, a mixture of propane, propylene, n-butane and isobutylene produce desirable results. The data hereinbelow indicate that the gasoline yields obtained when using isobutylene as the outside gas are considerably greater than when n-butane or no outside gas is employed. When no outside gas is employed, as the data show, higher temperatures are required to obtain maximum yields of gasoline than the temperatures at which maximum yields of gasoline are obtained in my process.

The purpose of using the outside gas or gases is to aid in the production of gasoline in the process. I am not certain how this penomenon occurs. It may be explained by the presence of the outside gas suppressing the cracking of the gas oil and the consequent formation of light gases. It may also be explained by the reaction of the outside gas in the reaction zone to form higher molecular weight hydrocarbons boiling within the gasoline range. I do not intend to limit my invention to either of these explanations, and the improved results obtainable from the use of an outside gas will be obvious from the data set forth hereinbelow.

The mol ratio of outside gas to gas oil in my process is within the range of 0.1:1 to 20:1. The preferable mol ratio is within the range of 0.5:1 to :1.

The catalyst for my process is an alumina-base cracking catalyst. Such catalysts as bauxite, bauxite impregnated with chromium oxide, ad-

sorbent clays, such as iullers earth, and acid activated bentonite clays are effective. Activated alumina and alumina, either alone or impregnated with other metallic oxides, such as chromium oxide, can be used in my process. However, I prefer to use catalysts of the synthetic silicaalumina type prepared by co-precipitating aluminum hydroxide and hydrous silica, followed by calcining or by treating a partially dried hydrous silica gel with an aqueous solution of an aluminum salt, such as aluminum chloride or aluminum sulfate, followed by Washing and drying or prepared in any other known manner. If desired, the synthetic silica-alumina catalysts may be promoted with an oxide of a metal of group VI of the periodic'system, for example, chromium oxide, but I prefer the unpromoted synthetic silica-alumina catalysts.

The gasoline resulting from my process is water-white in color, and upon standing for several months the gasoline retains this color. Gasoline prepared by the conventional catalytic cracking of gas oil obtained from shale oil has a similar color. However, Within three days time this gasoline assumes an opaque dark brown to black color. Redistillation produces a water-White gasoline, but within three days the color of this gasoline again deteriorates and it assumes the same opaque dark brown to black color. It is generally accepted in the art that a water-white gasoline that retains its light color is much more desirable than a similar gasoline that, in a short time, becomes discolored. This discussion demonstrates one of the main advantages of my process.

'I'he accompanying drawing represents a preferred method of eiecting my process. Such conventional equipment as valves, compressors, heating and cooling means, temperature and pressure recording and control devices, iiow control devices, and the like, are intentionally omitted, but the inclusion of such conventional equipment is within the skill of the art. Referring now to the accompanying drawing, oil sha-le enters retort i via line 2 where oil is thermally removed from the shale. Spent shale is removed from the system via line 3, and crude shale oil passes from retort i via line l to fractionator 5 where the crude shale oil is fractionally distilled to obtain the light gases overhead, a, gasoline fraction as a sidestream and a heavier gas oil fraction. Light gases are removed from fractionator 5 via line 6 and thence passed to suitable purication means l for removal oi hydrogen, carbon monoxide, carbon dioxide, methane, ethane, ethylene, nitrogen, ammonia, hydrogen sulide, and any other gases not desired in the outside gas for the catalytic polyforming reaction. Saturated and unsaturated hydrocarbons containing three and four carbon atoms per molecule are passed via lines 8 and Q to catalytic polyforming zone i0. A gasoline fraction boiling below 200 C. is withdrawn from fractionator 5 via line Il, and gas oil higher boiling than said gasoline fraction passes to zone l0 via line 9. An outside gas containing unsaturated and saturated C3 and C4 hydrocarbons is introduced to line 9 via line l2 and thus to zone l0 where the gas oil and outside gas are passed through a xed bed of a synthetic silica-alumina catalyst at catalytic polyforming conditions. The reaction effluent from Zone l0 is passed via line i3 to fractionator I4. The overhead gas from iractionator i 4 is removed via line l 5 and then recycled to zone l0 via lines I2 and 9. This overhead gas contains hydrocarbons having less than five carbon atoms per molecule, and, since only C3 and C4 hydrocarbons are preferred as Voutside gas in zone I0, a portion or all oi the gases in line I 5 are passed via line IS to hydrocarbon separator Il where Ci and Cz hydrocarbons are removed and Withdrawn via line I8. Separator Il may be a charcoal adsorber or any other suitable means for separating C1 and C2 hydrocarbons from Cs and C4 hydrocarbons. The hydrocarbons removed via line I8 are valuable as a fuel. and, if desired, they are passed (by means not shown) to retort I Where they are burned to supply heat necessary for driving on Jthe oil from the shale. C3 and C4 hydrocarbons pass from separator I'I via line I 9 to line I5, and they are thence recycled to Zone I0. Gasoline having an end point of 200 C. is Withdrawn .from fractionator I4 as a sidestream via line 20. rIlhis gasoline is Water-White in color, and, upon standing or in storage, this gasoline retains this color. However, gasoline thus obtained has a relatively high gum content, and it is usually desirable to treat the gasoline to remove the gum. One method involves washing the gasoline with a 10 per cent caustic soda solution followed by Washing with sulfuric acid solutions of l0 per cent and 98 per cent concentrations. As bottoms product from fractionator I4 is obtained a recycle oil boiling above 200 C., and this recycle oil is returned to zone Ill via lines 2| and 9. Since this recycle oil contains tar and other relatively high boiling hydrocarbons, it is usually desirable to pass at least a portion or all of the recycle oil in line 2| via line 22 and tar separator 23 prior to its return to zone I t via lines 24, 2l and 0. Tar and high boiling hydrocarbons are separated from the system via line 25.

The following examples are illustrative of my invention.

Example I A series of runs were made at atmospheric pressure charging a shale oil fraction having a boiling range of 260 to 340 C'. without any outside gas. A fixed bed catalytic reactor was ernployed containing synthetic silica-alumina catalyst. At an average reactor temperature or 573 C. and at a liquid space velocity of 0.67 liquid volumes of gas oil per volume of catalyst per hour, the maximum yield of gasoline, 27.1 per cent, based on the gas oil charged, Was obtained.

Example II To the same reactor containing a similar catalyst was charged shale oil of the same boiling range containing 0.7 part by weight of isobutylene per part of shale oil, The reactor pressure was maintained at 900 pounds per square inch gauge. Maximum yields of gasoline, 34.0 'per cent, based on the gas oil charged, were obtained at 443 C. `with a space velocity of 0.05 liquid volume of gas oil per volume of catalyst per hour and also at 464 C. with a space velocity of 4.0 liquid volumes of gas oil iper volume of catalyst per hour,

Example III To the same reactor containing a similar catalyst was charged shale oil of the same boiling range containing 0.7 part by Weight oi n-butane per part of shale oil. The reactor pressure was maintained at 900 poimds per square inch gauge. The maximum yield of gasoline, 24.4 per cent, based on the gas oil charged, was obtained at 481 C. and 0.54 liquid volume oi gas oil per volume of catalyst per hour.

Gasoline samples from the above runs were treated chemically by Washing withal),4 per cent caustic soda solution and then with l0 per cent and 98 per cent sulfuric acid solution. Upon completion oi the chemical treatment, all the samples were water-white in color. Within three days the gasoline prepared in Example I was opaque, dark brown to black in color. Redistillation produced a water-White gasoline which again turned black Within three days. The gasoline samples resulting from Examples II and III were also water-White in color, and there has been no deterioration in color over a period of several months.

From the abo-ve data the advantages of my process are obvious. Conventional methods of treating shale oil do not produce commercially useful gasoline, but the gasoline resulting from my process is of marketable quality. When using isobutylene as the outside gas, the maximum yield of gasoline is 25.4 per cent greater than the maximum yield obtained by conventional catalytic cracking of the shale oil. F111'- thermore, in my process maximum yields of gasoline are obtained at temperatures below 500 C., but in conventional catalytic cracking temperatures Well above 500 C. are often required to obtain maximum yields of gasoline. Also, in spite of the lower temperature, maximum yields are obtained in my process at space velocities considerably higher than the space velocities required for maximum yields in catalytic cracking of shale oil.

Numerous modifications of my invention Within the scope thereof will be apparent to those skilled in the art from the above disclosure.

I claim:

l. The process for producing a gasoline fraction from shale oil which comprises contacting a gas oil fraction of shale oil with an aluminabase cracking catalyst in the presence of a normally gaseous hydrocarbon containing no more than four carbon atoms per molecule at a temperature Within the range of 200 to 700 C. and at a superatmospheric pressure, and recovering a color stable gasoline fraction thus produced.

2. The process for producing a gasoline fraction from shale oil which comprises contacting a gas oil fraction of shale oil boiling within the range of to 450 C. with .an alumina-base cracking catalyst in the presence of a normally gaseous hydrocarbon containing from three to four carbon atoms per molecule at a temperature within the range of 200 to '700 C. and at a pressure Within the range of 300 to 2500 pounds per square inch, and recovering a gasoline fraction which does not deteriorate and darken in color.

3. The process for producing a gasoline fraction from shale oil which comprises contacting a gas oil fraction of shale oil boiling Within the range of 150 to 450 C. with a synthetic silicaalumina catalyst in the presence of a` hydrocarbon containing four carbon atoms per :molecule .at a temperature within the range of 200 to 700 C. and at a pressure within the range of 300 to 2500 pounds per square inch, and recovering a gasoline fraction which does not deteriorate and darken in color.

4. The process for producing a gasoline fraction from shale oil which comprises contacting a gas oil fraction of shale oil boiling within the range of 150 to 450 C. With a synthetic silicaalumina catalyst in the presence of a hydrocarbon gas containing four carbon atoms per molecule with a molar ratio of hydrocarbon gas to gas oil Within the range of 0.1:1 to 20:1 with a liquid space velocity of gas oil of 0.2 to 20 liquid volumes of gas oilper volume of catalyst per hour at a temperature Within the range of 200 to '700 C. and yat a pressure Within the range of 300 to 2500 pounds per square inch, and recovering a gasoline fraction which does not deteriorate and darken in color.

5. The process for producing a gasoline fraction from shale oil which comprises contacting a gas oil fraction of shale oil boiling Within the range of 150 to 450 C. with a synthetic silicaalumina catalyst in the presence of butane With a molar ratio of butane to gas oil Within the range of 0.1:1 to 20:1 with a liquid space Velocity of gas oil of 0.2 to 10 liquid volumes of gas oil per volume of .catalyst per hour at a temperature Within the range of 200 to 500 C. and at a pressure within the range of 800 to 1500 pounds per square inch, and recovering a gasoline fraction which does not deteriorate and darken in color.

6. The process for producing a gasoline iraction from shale oil Which comprises contacting a gas oil fraction of shale oil boiling Within the range of 150 to 450 C. with .a synthetic silicaalumina catalyst in the presence of isobutylene with a molar ratioy of isobutylene to gas oil Within the range of 0.1:1 to 20:1 with a liquid space velocity of gas oil of 0.2 to 10 liquid volumes of gas oil :per volume o1' catalyst per hour at a temperature Within the range of 200 to 500 C. and at a pressure Within the range of 800 to 1500 pounds per square inch, and recovering a gasoline fraction which does not deteriorate and darken in color.

7. A process according to claim 6 wherein the molar ratio of isobutylene to gas oil is Within the range of 0.5:1 to 10:1.

LLOYD BERG.

References Cited in the le of this patent UNITED STATES PATENTS i Number Name Date 1,629,908 Faragher et al. May 24, 1927 2,249,924 Wilson July 22, 1941 2,308,792 Thomas Jan. 19, 1943 2,415,537 Schulze et a1. Feb. 11 1947 

1. THE PROCESS FOR PRODUCING A GASOLINE FRACTION FROM SHALE OIL WHICH COMPRISES CONTACTING A GAS OIL FRACTION OF SHALE OIL WITH AN ALUMINABASE CRACKING CATALYST IN THE PRESENCE OF A NORMALLY GASEOUS HYDROCARBON CONTAINING NO MORE THAN FOUR CARBON ATOMS PER MOLECULE AT A TEMPERATURE WITHIN THE RANGE OF 200 TO 700* C. AND AT A SUPERATMOSPHERIC PRESSURE, AND RECOVERING A COLOR STABLE GASOLINE FRACTION THUS PRODUCED. 